Caption: Basal cell carcinoma. Close-up of a skin tumour on the cheek of an elderly man. This cancer is known as basal cell carcinoma, or rodent ulcer. It commonly occurs on the face or neck region, typically affecting fair-skinned people over age 50. Direct skin damage from ultraviolet radiation in sunlight is thought to be the cause in most cases. Basal cell carcinoma usually appears as a small, flat nodule growing slowly, which then breaks down at the centre to form a shallow ulcer. The tumour may invade deeper tissues if untreated. It may be removed by cryosurgery or radiotherapy or with a surgical operation. Treatment usually results in a complete cure.